1. Field of the Invention
This invention relates to mechanical harvesting of vegetable crops, particularly leafy green vegetables and other crops which do not grow in discrete marketable units as do celery, head lettuce, cabbage, etc. Whether harvested by hand or mechanically, leafy vegetables are conventionally field collected in bulk bins. Prior to sale to the consumer, they must be manually bound separately into bunches of uniform size.
2. Description of the Prior Art
A basic mechanical vegetable harvester is disclosed in The Grower publication ("Once-Over Harvester Has Universal Application," pp. 916-917, May 14, 1966). This device employs a pair of rubber-faced lifting belts pressed tightly together to grip the leafy tops of the plants as they are uprooted or cut at the ground. The lifting belts feed the plants to a conveyor across the rear of the tractor which delivers them into boxes, sacks, or trailers. A similar harvester is shown in Krier et al. (U.S. Pat. No. 2,855,058) wherein the leaves are gathered, cut from the plants, and conveyed upward to a bushel basket by means of parallel endless belts. In another vegetable harvester taught by Medlock et al. (U.S. Pat. No. 3,989,110) green onions are raised from the ground and conveyed through a series of gripping belt assemblies to a receiving tray for subsequent manual sorting and bundling. U.S. Pat. No. 3,968,842 granted to Puch et al. shows a tomato plant harvester wherein parallel gripping belts lift the plants from the ground and convey them to an expandable compartment of a receiving box. Sensing switches actuate mechanisms for expanding the compartment and for shifting an empty box into the position of one that has been filled. Mayo et al. (U.S. Pat. No. 3,743,024) also shows harvesting seedling plants and packing them into shipping cartons. In Rath (U.S. Pat. No. 4,037,666) leafy and woody plants are uprooted and guided along a path by endless conveyor bands to a bundling device. A photosensitive element counts the individual plants exceeding a minimum size standard and actuates the bundling device when a predetermined number has been collected.
A characteristic problem with the aforementioned vegetable harvesters is that they lack the facility to segregate the cut vegetable leaves into uniform bunches which can be shipped directly to the market shelf without further manual handling. Most leafy green vegetables are grown closely together in rows and have substantial variation in leaf size. When they are conveyed to the collecting station as a continuous line of leaves, counting devices such as that employed by Rath would be totally ineffective. The loading boxes of Puch et al. and Mayo et al. are designed for bulk packing, and the sensing mechanisms therein are not sufficiently sensitive to bundle the greens into marketable units.